Lewis Acid-Mediated Friedel-Crafts-Type Formylation of Alkenes with Dichloromethyl Methyl Ether in the Presence of Pyridines.

Various alkenes are formylated with dichloromethyl methyl ether (MOMCl) by the combined use of SnCl/2,6-dibromopyridine () or AgOTf/pyridine () via Friedel-Crafts-type reaction. The former reagent combination is mainly applied to α,α-diarylalkenes, while the latter one is applied not only to arylalkenes but also to some alkylalkenes. Vinyl aldehydes are exclusively obtained from alkenes that can possibly afford both allyl and vinyl aldehydes.

Synthesis of Azadioxa-Planar Triphenylboranes Bridged by Aryl- and Alkylimino Groups and Their Photophysical Properties.

Heteroatom-bridged planar triphenylboranes, in which the three phenyl groups are bridged at the positions by heteroatoms, are attracting growing attention as one of the heteroatom-containing π-conjugated molecules. Herein, we developed the synthetic method of planar triphenylboranes bridged by two oxygen atoms and one nitrogen atom, and the substituent on the nitrogen atom is derived into various aryl and alkyl groups. A key intermediate bearing an imino group (-NH-) was synthesized from a bis-triflate precursor bridged by two oxo groups via a nucleophilic aromatic substitution reaction of benzyl amine and following debenzylation.

Inclusion of Amine Isomers with Open-Chain Hosts Having a Partial Structure of Butylthiacalixarene.

Porous materials, which can capture a specific compound from a hard-to-separate molecular mixture, are strongly desired for practical separation and purification processes. Aiming to develop such materials, we have investigated the performance of our original host compounds, [3,3'-thiobis(5-butyl-2-hydroxybenzene)-1,1'-diyl]diacetic acid () and its monopropyl ester (), in discriminating among regio- or stereoisomers of three groups of amines, 2-, 3-, and 4-methylpyridine, 2-, 6-, and 8-methylquinoline, and and 4-cyclohexanamine. Diacid selectively included 4-methylpyridine in hexane and 3-methylpyridine in toluene in competitive inclusion among the three regioisomers.

Extraction of Pd(ii) and Pt(ii) from aqueous hydrochloric acid with 1,3-diaminocalix[4]arene: switching of the extraction selectivity by using different extraction modes.

The extraction ability of 1,3-diaminocalix[4]arene (2: HL) toward platinum group metals (PGMs) has been investigated, which revealed that 2 is able to extract Pd(ii) and Pt(ii) from hydrochloric acid different extraction modes. The extraction species for Pd(ii) and Pt(ii) are [PdL] and [PtCl(HL)], respectively, as evidenced by equilibrium analysis and X-ray crystallography. In [PdL], the two phenoxide oxygens and two amino nitrogens of L coordinate to the Pd ion.

Acylation of Alkenes with the Aid of AlCl and 2,6-Dibromopyridine.

Friedel-Crafts-type acylation of alkenes with acyl chlorides has been successfully conducted with a wide substrate scope by the combined use of AlCl and 2,6-dibromopyridine. Trisubstituted alkenes afford allylketones or vinylketones depending on the presence or absence of hydrogen atom(s) at the β-position to the acylation site, while monosubstituted alkenes exclusively afford vinylketones.

Electrophilic Borylation of Terminal Alkenes with BBr/2,6-Disubstituted Pyridines.

A variety of terminal alkenes, as well as heteroaromatic compounds, are borylated by the combined use of BBr/2,6-dichloropyridine (B3) or BBr/2,6-lutidine (B5). α,α-Diarylalkenes prefer the former reagent combination, while other alkenes prefer the latter. Mechanistic considerations strongly suggest that the former and latter reactions proceed through electrophilic substitution reactions with BBr and [BBr·B5]BBr, respectively.

Design and Synthesis of Open-Chain Hosts Having a Partial Structure of p-tert-Butylthiacalixarene.

The development of separation materials for hard-to-separate molecular mixtures is highly desired from environmental and economic perspectives. Although the crystal of p-tert-butylthiacalix[4]arene exhibits high guest selectivity in inclusion from a mixture of molecules with similar sizes and shapes, it cannot include molecules larger than its calix cavity. To extend its guest inclusivity, we designed and synthesized an open-chain host, [3,3'-thiobis(5-tert-butyl-2-hydroxybenzene)-1,1'-diyl]diacetic acid (4).

Identification of number and type of cations in water-soluble Cs and Na calix[4]arene-bis-crown-6 complexes by using ESI-TOF-MS.

The treatment of cesium-contaminated wastewater has become one of the biggest issues. The selective Cs removal from wastewater containing competitive alkali metal ions such as Na is desired to reduce the volume of sludge. Therefore, the present work focused on water-soluble calix[4]arene-bis-crown-6 (W-BisC6) to selectively capture Cs.

EtAlCl2/2,6-Disubstituted Pyridine-Mediated Carboxylation of Alkenes with Carbon Dioxide.

α-Arylalkenes and trialkyl-substituted alkenes undergo carboxylation with CO2 in the presence of EtAlCl2 and 2,6-dibromopyridine to afford the corresponding α,β- and/or β,γ-unsaturated carboxylic acids. This reaction is suggested to proceed via the electrophilic substitution of EtAlCl2 with the aid of the base, followed by the carbonation of the resulting ate complex. This reaction can be applied to terminal dialkylalkenes by using a mixture of 2,6-di-tert-butylpyridine and 2,6-dibromopyridine.

Photoracemization of Blestriarene C and Its Analogs.

Two analogs of blestriarene C (4,4'-dimethoxy-1,1'-biphenanthrene-2,2',7,7'-tetraol) bearing no 7,7'-dihydroxy (3) and 4,4'-dimethoxy groups were prepared. Unlike blestriarene C (1), compounds and , as well as 1,1'-biphenanthrene-2,2'-diol (5), do not racemize under fluorescent lamp illumination. Cyclic voltammetry analysis reveals that compound has a lower half-wave potential (E(1/2)) than compounds , suggesting that a redox cycle is involved in the racemization.

1,3-Diiodocalix[4]arene: synthesis by Ullmann-type iodination of 1,3-bistriflate ester of calix[4]arene, conformational analysis, and transformation into 1,3-dicarboxy-, diformyl-, and dialkylcalix[4]arenes.

A facile synthesis of 1,3-diiodocalix[4]arene 6 has been achieved by copper-catalyzed iodination of the 1,3-bistriflate ester 2a of p-tert-butylcalix[4]arene. After protection of the hydroxy groups with iodomethane, diiodide 6 is subjected to halogen–lithium exchange with butyllithium, followed by carbonation with CO2 or formylation with N-formylpiperidine and subsequent deprotection of the hydroxy groups to give novel dicarboxylic acid 11 or dialdehyde 16 in practical yields. The iodo groups of diiodide 6 pass through the calixarene macrocycle; the activation free energy for the conversion of the more stable syn conformer 6syn to the less stable anti conformer 6anti is ΔG(⧧) = 104 kJ mol(–1) at 298 K.

Effect of solvent polarity on enantioselectivity in Candida antarctica lipase B catalyzed kinetic resolution of primary and secondary alcohols.

The Candida antarctica lipase B (CAL-B) catalyzed kinetic resolution of primary and secondary alcohols via acetylation is dependent on the permittivity (ε) of the reaction solvent. For example, the enantiomeric ratio (E) vs ε plot for the acetylation of 1-(naphth-2-yl)ethanol (1) exhibits a convex shape, taking the maximum E value at a medium ε value (11.2), whereas the same plot for the acetylation of benzyl 3-hydroxybutylate (3) exhibits a concave shape, taking the minimum E value at a similar ε value (11.

Switching of the diastereomer deposited during the crystallization of N-[(S)-1-phenylethyl]-2'-carbamoyl-1,1'-binaphthalene-2-carboxylic acid: investigation of the mechanism of dielectrically controlled resolution.

Dielectrically controlled resolution (DCR) has been achieved during the crystallization of (S)-1-phenylethylamides of racemic 1,1'-binaphthalene-2,2'-dicarboxylic acid (RS(a),S)-1. For example, a water well-shaped plot is obtained for the diastereomeric excess (de) of the deposited amide versus the solvent permittivity (ε) for the crystallization of (RS(a),S)-1 from three-component mixed solvents, consisting of 25 vol % of dichloromethane and 75 vol % of varying ratios of two solvents (i.e.

Unique inclusion properties of crystalline powder p-tert-butylthiacalix[4]arene toward alcohols and carboxylic acids.

Powdery crystals of p-tert-butylthiacalix[4]arene (2) selectively include EtOH from 1:1 mixtures of MeOH-EtOH and EtOH-PrOH, and EtCO(2)H from HCO(2)H-EtCO(2)H. On the other hand, no acid is included from HCO(2)H-MeCO(2)H, even though MeCO(2)H is included from the neat acid. The origins of these phenomena are discussed based on X-ray analysis of inclusion crystals prepared separately by crystallization.

Synthesis of mono- and 1,3-diaminocalix[4]arenes via Ullmann-type amination and amidation of 1,3-bistriflate esters of calix[4]arenes.

Practical methods are described for the preparation of monoamines 4 and 1,3-diamines 5, bearing one or two amino group(s) instead of the hydroxy group(s) at the 28-position or at both the 26- and 28-positions of p-tert-butylcalix[4]arene (1a) and p-tert-butylthiacalix[4]arene (1b), via the Ullmann-type amination or amidation. Thus, the copper-catalyzed or mediated amination of the 1,3-bistriflate ester (2a) of 1a with benzylamine affords either mono(benzylamino) triflate 7a or 1,3-bis(benzylamine) 8 in a high yield, depending on the reaction conditions. On the other hand, the 1,3-bistriflate ester (2b) of 1b resists disubstitution and produces, under stoichiometric conditions, mono(benzylamino) triflate 7b.

Direct carboxylation of arenes and halobenzenes with CO2 by the combined use of AlBr3 and R3SiCl.

The Lewis acid-mediated direct carboxylation of aromatic compounds with CO2 is efficiently promoted by the addition of silyl chlorides bearing three alkyl and/or aryl substituents in total on the silicon atom. Thus, toluene, xylenes, mesitylene, and some other alkylbenzenes are treated with a 1:1 mixture of AlBr3 and Ph3SiCl in neat substrates under CO2 pressure (3.0 MPa) at room temperature, to give the corresponding carboxylic acids in 60-97% yields, based on AlBr3.

Synthesis of dinuclear boron complexes of sulfinylcalix[4]arenes: Syn/Anti stereocontrol by the arrangement of the sulfinyl functions.

Stereocontrol in the synthesis of dinuclear metal complexes of sulfinylcalix[4]arenes 2 has been achieved by the arrangement of sulfinyl functionalities. Thus, the treatment of the(rtct) isomer of 2 (2(rtct)) with an excess of Et(3)B affords syn dinuclear boron complex 4, while a similar treatment of rctt and rcct isomers 2(rctt) and 2(rcct) yields anti dinuclear complexes 5 and 6, respectively.

Simple and effective 3D recognition of domoic acid using a molecularly imprinted polymer.

We have developed a simple and effective molecular imprinting technique to target compounds with flexible structure. Domoic acid (DA), an amnesic shellfish poison, was used as the target compound while many acidic compounds (mono-, di-, and tricarboxylic acids) were used as template molecules for molecularly imprinted polymers (MIPs). Evaluation of selective recognition abilities using liquid chromatography revealed that the highest selective recognition ability for DA was found when pentane-1,3,5-tricarboxylic acid (1,3,5-PeTA) was used as the template.

Conformational behaviors of tetra-O-methylsulfinylcalix[4]arenes--an approach to control the conformation of thiacalix[4]arenes by oxidizing sulfur bridges.

The conformational behaviors of all four stereoisomers [5(rctt), 5(rcct), 5(rtct), and 5(rccc)] of tetra-O-methylsulfinylcalix[4]arene were studied by the 1H NMR spectroscopic method. Variable-temperature (VT) NMR experiments of 5(rctt), 5(rcct), and 5(rtct) revealed that each compound adopted the same conformation as that in the crystals at low temperatures and exhibited a self-exchange between the two equivalent species of this conformation at elevated temperatures. The values of the activation enthalpy DeltaH for the self-exchange were similar (approximately 70 kJ mol-1).

Two-dimensional supramolecular arrangements of enantiomers and racemic modification of 1,1'-binaphthyl-2,2'-dicarboxylic acid.

Formation of adlayers of the optically active compound 1,1'-binaphthyl-2, 2'-dicarboxylic acid (BINAC) on iodine-modified Au (111) surfaces in perchloric acid was investigated by in situ scanning tunneling microscopy (STM). Highly ordered arrays formed on the surfaces via simple spontaneous adsorption from a solution of enantiomers or the racemic BINAC, in spite of the fact that BINAC has a three-dimensionally complex stereochemical structure. Adlayers of both enantiomers essentially shared the same enantiomorphous structure.

Epimerization of diastereomeric alpha-amino nitriles to single stereoisomers in the solid state.

[reaction: see text] A diastereomeric mixture of the alpha-amino nitrile prepared by the Strecker reaction of benzaldehyde, (1S,2R)-1-aminoindan-2-ol, and cyanotrimethylsilane thermally epimerizes in the solid state to give a single diastereomer with an (S)-configuration at the alpha position to the nitrile moiety. This shows a sharp contrast to the reaction conducted in DMSO at room temperature, which gives a 1:1 mixture of (S)- and (R)-isomers. Several other alpha-amino nitriles also epimerize in the solid-state toward single diastereomers.

Stereoselective dialkylation of the proximal hydroxy groups of calix- and thiacalix[4]arenes.

Treatment of p-tert-butylcalix[4]arene (C1) and its sulfur-bridged analog T1 with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in the presence of imidazole gives proximally O,O'-disiloxane-1,3-diyl-bridged calixarenes C2 and T2 in excellent yields, respectively. Subsequent base-catalyzed etherification of the remaining hydroxy groups with alkyl halides gives syn- and anti-O'',O'''-dialkylated products, the stereoselectivity of which varies depending on the nature of the macrocycle, as well as the metal cation of the base employed. Thus, conventional calixarene C2 preferentially affords syn compounds of 1,2-alternate conformation (C3) with the aid of tert-BuOK and K(2)CO(3) and anti counterparts of partial-cone conformation (C4) with Cs(2)CO(3).

Synthesis of all stereoisomers of sulfinylcalix[4]arenes.

All four stereoisomers of p-tert-butylsulfinylcalix[4]arene [4(rccc), 4(rcct), 4(rctt), and 4(rtct)], arising from the disposition of the four sulfinyl groups with respect to the mean plane of the four bridging sulfur atoms, have been prepared via oxidation of p-tert-butylthiacalix[4]arene (2) or its tetra-O-benzyl ethers 5 of defined conformations. Thus, treatment of 2 with 4.4 molar equiv of NaBO(3).